1. Field of the Invention
The present invention relates to a light-emitting device, a backlight device, and an image display apparatus.
2. Description of the Related Art
A liquid crystal panel is a non-self-luminous display panel and thus includes a backlight device as a light-emitting device that emits light to the backside of the liquid crystal panel.
The backlight device includes a light source (light-emitting unit), a reflecting plate, a group of optical sheets, and the like. A direct-type backlight device in which LEDs are used as a light source and are arranged in a planar form and at equal intervals so as to be parallel to a group of optical sheets is known.
Light emitted by LEDs has directional characteristics and tends to concentrate on the front surface. Thus, in order to improve the brightness uniformity of a liquid crystal panel, the distance (diffusion distance) between the LEDs and the group of optical sheets needs to be longer than an arrangement interval of the LEDs. As a result, the thickness of the backlight increases.
However, due to market trends in recent years, the backlight needs to be made thinner.
If the diffusion distance is decreased only to make the backlight thinner, brightness unevenness is visible on the display panel due to the directional characteristics of LEDs.
In order to eliminate the brightness unevenness, Japanese Patent Application Publication No. 2006-339148 forms a conical optical member between LEDs. When light emitted from a light source passes through the optical member, the light becomes more uniform. Japanese Patent Application Publication No. 2006-196456 discloses an example of CCFL.